I last went on a Bible study with a determined friend trying to "help" me in 2013, my last meeting was Memorial although I will go to accompany an elderly friend if she asks, so I dont fit your criteria of "still in" exactly.
What I wanted to comment on was that you are not the only one here fading very slowly and deliberately. There are quite a few of us.
I think you are doing a smart thing to be wherever your young children are. Think of it as your husband being deployed in a foreign country and you are making the best of it with your kids.
If you have to go out in service with your MIL is there anyway you could plea bargain it into accompanying her on a Bible Study?
That beats the heck out of door to door.
If you have to do door to door, could you take her for an iced coffee halfway through? Pleading summer heat?
OneEyedJoe is exactly right, it takes tens of thousands of hours and many love bombing JWs to get one person "in". You arent going to do any damage in a token morning with MIL.
You will however be bored, no doubt about it!